This invention is an improvement in part of the inventions described and claimed in my prior issued U.S. Pat. Nos. 4,305,192 and 4,137,006.
In these patents which are incorporated by reference in this disclosure in their entireties, composite horizontally and vertically split casings are described wherein a casing can be readily fabricated to any desired length using standard cast casing ends (inlet and outlet sections) and differing shell plate lengths. By varying the shell plate length the volume of the compressor is varied, while the pressure remains essentially constant. However where the pressure requirements for a casing change entire new casing inlet and outlet sections must be fabricated.
It is not believed that there is now commercially available standard cast inlet and outlet sections which may be easily modified to satisfy a pressure rating or design requirement within a range of pressure ratings. That is, once a pressure rating is established for a compressor, inlet and outlet sections are specifically fabricated.
The present invention is broadly directed to inlet and outlet sections which are used with horizontally or vertically split casings and which once fabricated may be easily modified to satisfy a specific pressure rating within a range of possible pressure ratings.
In the present invention, standard inlet and outlet sections are formed. That portion of each section which abuts the shell section is characterized by a variable-dimensioned extension. Further the sections include variable-dimensioned stub ends for inlet and outlet nozzles. The extensions can be modified to mate with a shell plate which shell plate is designed for a specific pressure rating and the stub ends can be modified to mate with specific inlet and outlet nozzles.
In many industries which require compressors of the type herein described, a typical pressure rating would be initially based on the shell section thickness and of necessity, the inlet and outlet sections of corresponding thickness to which it is welded. In some instances, the users of such compressors will request the manufacturers of the compressors to keep in stock matching sets of shells and inlet and outlet sections designed for various pressure ratings.
Each cylinder or compressor housing has unique design parameters and pressure parameters. Contained housings can vary in shape but probably over 95% used are cylindrical in shape. A simplified formula for pressure rating is: EQU Th=PR/SE or EQU P=ThSE/R
Th=wall thickness PA1 P=pressure in psi PA1 S=unit tensile strength for any given material (usually steel) PA1 E=weld joint efficiency PA1 R=radius of housing
The pressure formula, then: EQU P=ThSE/R
and, as a practical matter, the values of S and E are constant whereby P=Th/R, RP=Th. Thus, if R is held constant, say to 30 inch radius, then the wall thickness (Th) varies directly as the pressure. Therefore, where each has a wall thickness which varies basically with pressure, each compressor casing design is unique unto itself because of its pressure rating. Correspondingly the inlet and outlet nozzles will vary in internal diameter and wall thickness and the nozzles of the casings must be designed accordingly.
Each compressor casing must then require its own design, drawings, bills of material specifically unique to its own pressure, and each compressor casing of varying pressures must then have its own unique inventory, lead time, production standards, methods and test data.
The present invention overcomes the necessity to maintain in inventory a plurality of inlet and outlet sections covering all possible dimensions to accomodate various pressure designs as required by the ultimate user.